1. Field of the Invention
The invention relates to an actuator for flashing lights such as directional or emergency lights for vehicles. More specifically, the invention relates to a two-wire, electronic actuator.
2. Description of Prior Art
In the earliest approach, such actuators included two-wire electro-mechanical relays connected in series with both the power supply and the load (the flashing light). The relays were controlled by a timing device to close and open at a predetermined frequency, and, by applying power to the lights when the relay was closed, and removing power when the relay was open, the flashing light was caused to flash.
It is presently desirable to replace such relay-inclusive actuators with electronic actuators using semiconductor elements. Such electronic actuators have been developed but, typically, they comprise three-wire devices, i.e., two wires for connecting the actuators in parallel with the power supply and a third wire connected to the flashing light. Thus, in replacing the relay-inclusive actuators of presently existing vehicles, it is not simply a matter of removing the present actuator and replacing it with an electronic actuator. Instead, it is necessary to add a ground terminal to accept the three-wire replacement for the two-wire actuator.
In addition, electronic actuators are illustrated in U.S. Pat. No. 3,493,927, Effenberger, U.S. Pat. No. 4,173,013, Spiteri(1) and U.S. Pat. No. 4,876,526, Spiteri (2). The Effenberger patent teaches a system for connecting flashing lights to indicate direction by selection of the appropriate flashing light. Spiteri(1) teaches an actuator which uses an operational amplifier to increase the intensity and the life of the flashing lights. The Spiteri(2) teaches an actuator wherein the flashing frequency is controlled by a CMOS oscillator whose frequency is independent of the frequency of the power supply.